These phrases were all over headlines for the 2018 U.S. midterms. It’s hard to believe that less than twenty years ago they could have totally confused you. By now, the arbitrary color-coding of two political parties has become utterly axiomatic in American language and visual culture. There’s a reason those MAGA hats are crimson.

Workers walk on a giant presidential election map of the United States made of ice in the skating rink at New York City’s Rockefeller Center, in 2004. The states in red went for President Bush, the blue states for Senator John Kerry, and the remaining white states were undecided as of about midnight on election night. (Kathy Willens/AP)

And guess what? A map did it. Our partisan palette—blue for Democrats, red for Republicans—originated in the election maps the media produced for the 2000 presidential race.

Previously, TV stations, newspapers, and political atlases mostly followed their own aesthetic whims when it came to coloring thematic election maps, which date back to the 19th century. Sometimes they threw yellow and green in the mix, which would now seem totally blasphemous, though red and blue, being the hues of the American flag, have always been popular picks. But their respective assignments have varied; blue just as often repped Republicans and red, Democrats, through the end of the 20th century. And, confusingly, in other countries, the fiery shade is usually associated with leftist parties. That was sometimes the case in the U.S. ''It's beginning to look like a suburban swimming pool,'' one television anchor reportedly said in November 1980, as Ronald Reagan’s landslide victory over Jimmy Carter became manifest in a blue-tiled map.

A late-19th century map of the presidential elections of the United States, 1789 to 1876. Democrats are the party in yellow, and the Know-Nothings are blue. Republicans are, in fact, red. (Library of Congress)

But the turn of the millennium was another fraught time in American politics. It took weeks for the nation to learn whether George Bush or Al Gore had won the presidency, as poll workers recounted the ballots in Florida. Because electoral maps were on screen and in print so often, producers and publishers figured consistency would help viewers follow along. So they conformed to the same colors, and from that point on, they really, really stuck. That’s how you automatically knew the “red tide” wasn’t some kind of biblical meteorological event—although the elections did sometimes feel like that.

Does our two-sided color-wheel have any effect on our political affinities? A color psychologist told the New York Times in 2004 that it’s hard to say if people are more drawn to something by its associated color. But one 2016 study published by the National Institutes of Health suggests colors can drive parties apart. Psychology researchers tested how readers reacted to news articles about Russia and NATO when each subject was represented on a map as red and blue, respectively (their old Cold War-era designations), compared to how they perceived other color combinations.

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The result: Participants who already had negative beliefs about Russia read the sides as being more antagonistic, but only when Russia was depicted in red. In other words, the colors reinforced political perceptions and stereotypes. Somehow, it’s not hard to imagine the same is true of the un-united red and blue states.

A cartographic feast

Elections are always a feast for map nerds, and these midterms were no exception. On CityLab, several recent stories have used maps to highlight what was at stake on Tuesday.

Up first, I wrote about a map by the amateur cartographer Philip Kearney that put a twist on voter turnout rates for the 2016 presidential election. Kearney showed how if no-show eligible voters had cast their ballots for “nobody”—the effective result of their abstention—“nobody” would have won the election rather than either of the actual candidates. And in a new series of interactive maps, Esri dug up more election data to show how non-voters helped elect Donald Trump.

Democrats had their turn at kicking off a new normal on Tuesday night, too, by taking control of the House with a “sweeping performance in suburban congressional districts,” Montgomery told me later. He writes for MapLab:

Democrats won 13 “sparse suburban” districts and another nine “dense suburban” districts, as categorized by CityLab’s Congressional Density Index. Democrats also won most of the remaining Republican-held urban districts, but made few gains into rural districts where they are a distinct minority.

About the Author

Laura Bliss is CityLab’s West Coast bureau chief. She also writes MapLab, a biweekly newsletter about maps (subscribe here). Her work has appeared in The New York Times, The Atlantic, Los Angeles magazine, and beyond.